The present invention relates to the field of caps intended to be connected to the threaded neck of a bottle or a container, in order to transfer a liquid, pasty or powdered additive, for example an organoleptic supplement, a mineral, a colouring agent, a taste additive or a chemical supplement, for example a catalyst, a reagent or a detergent, into the contents of the bottle or of the container. The contents of the measuring cap is intended to be mixed with the contents of the container or of the bottle whereon it is placed, or to recharge the container.
To allow an easy use of such measuring caps, they must reduce handling and ensure a perfect sealing both during the phase of positioning on the container and during the phase of transfer of the dose contained in the measuring cap.
Various solutions for the production of such devices, are known in the prior art especially for the production of measuring caps.
The German Patent DE102004013270 is known in the prior art, which describes a fitting to be screwed onto the neck of a bottle and provided with a membrane. This membrane is connected to the inner annular surface of the fitting by an annular zone having a reduced thickness. When the fitting is screwed onto the bottle neck, the front zone of the neck comes into contact with the membrane and not with the annular peripheral area having a reduced thickness and exerts an axial force causing the tearing of this annular area in an uncontrolled manner up to the tearing thereof. The membrane is then released and the neck goes into the fitting.
This solution provides for the sealing at the bottom of the thread which is not adapted to hold the contents of the fitting during the various handlings of the system.
The US patent application US2010/301002 is also known in the prior art, which describes a measuring cap for a product to be added to a liquid contained in a container with a neck adapted to receive a screwed cap comprising:                a first crown-cap-shaped part having a bottom and a lateral skirt, the end opposite the bottom of which is provided with an inner thread        a second cup-shaped part with a bottom and a side skirt.        
The cup and the crown-cap have first snapping means which cooperate to hold the cup in the membrane in a first relative axial position with a sealed peripheral contact therebetween.
A spacer extending inside the cup skirt from the bottom thereof towards the bottom of the crown-cap to form a stop limiting the sinking of the cup into the crown-cap beyond the first position. This spacer is a means for breaking the bottom of the cup when the insertion of the latter into the crown-cap is forced beyond said first position by the sealing surface of the neck.
This solution raises sealing problems due to the sliding of the crown-cap relative to the cup.
Furthermore, the spacer occupies the useful volume and therefore reduces the capacity of the measuring cap. It can also deform upon screwing, and thus not efficiently execute its punching part.
Also known is the document US2008/142471 which describes another example of a measuring cap.
The patent application US2007/079895 discloses another exemplary bottle comprising a water tank, a threaded neck and an upper tank. The upper tank has an upper part, a lower part removably attached to the upper part, a cylindrical coupling element protruding downwards from the lower part and comprising inner threads fixed to the neck, and a sealing gasket formed in an upper part of the coupling element and above the opening. In the alternative solution shown in FIGS. 5 and 6 in this document, a hollow element punches a membrane, when the user presses the top of the upper elastomer tank.
Many of the prior art solutions provide for a finger positioned in the interior volume of the measuring device, exerting a stress on a membrane when screwing the measuring device onto the container neck.
These solutions have several drawbacks. First, the volume of the finger reduces the useful volume, and requires to increase the overall size of the measuring device to compensate for the dead volume occupied by the finger.
Secondly, the production by plastic molding is complicated by this finger erected on the surface of the cap bottom.
Other solutions provide for a membrane surrounded by a break-off line torn when the measuring device engages onto the neck of the bottle and upon screwing.
These solutions are not satisfactory either, because the membrane is released after breaking, and may penetrate into the bottle, or move into a position where it becomes an obstacle in the flow of the contents of the measuring device into the bottle, besides sealing is no longer ensured at the sealing surface or at the top of the bottle ring, which results in a loss of the contents of the fitting during the various handlings of the system.
Moreover, the solutions of the prior art have complex configurations requiring either the assembling of several parts, or an industrial production with complex molding tools, including sliding molds.
Eventually, in most solutions of the prior art, the devices have different parts in relative motion, which makes it difficult to obtain a good sealing.
To remedy these drawbacks, the present invention in its broadest sense relates to a measuring device consisting of a body defining an interior volume for receiving a liquid or powdered or pasty composition intended to be transferred to a container having a threaded neck, with said device having a skirt provided with a thread matching the thread of said container, and a membrane connected to the inner wall of said body by a peripheral zone having a generally annular shape characterized in that said peripheral zone has:                at least one break-off line        at least one area extending in a transverse plane, on the periphery of the membrane so configured as to cause the breaking of at least a part of said break-off line when it comes into contact with the front surface of the bottle neck.        
This peripheral area advantageously has the same or a greater thickness than that of the membrane, so as to prevent an uncontrolled tearing. When screwing, tearing does not occur on a peripheral area having a low thickness, but along a break-off line formed on the peripheral area.
Thus, when the rotation is started after both threads are engaged, the device engages around the bottle neck, and the transversal area gets closer to the front surface of the neck until the front region of the neck comes into contact with the annular peripheral region—not with the membrane. When screwing on, the front surface of the neck exerts an axial stress, perpendicular to this cross-sectional area of increasing magnitude, until it causes the tearing along the break-off line, which releases the membrane.
Advantageously, the device comprises a specifically arc-shaped stop, the median line of which has a radius R, where R substantially corresponds to the median radius of the threaded neck of said container, with said stop being so configured as to rest on the front surface of the bottle neck upon screwing the skirt onto the threaded neck of the container and a hinge region the median radius of which is greater than R.
“When screwing” means, in this patent, a phase of screwing engagement:                subsequent to the initiation of screwing, where the two threaded elements come into contact, and        prior to being stopped.        
This device is a single-block piece, molded in one piece without any insert (possibly except the bottom placed after filling the device). This makes it possible to solve the sealing problems encountered when assembling additional parts.
This single-block device is closed either by an attached bottom, or by a deformation of the part opposite the membrane, for sealing, rolling or closing the filling end by any known method.
The opening of the device is ensured by the striking of the membrane when the stop comes in contact with the front surface of the bottle neck. When screwing on, the protrusion exerts a mechanical force onto the membrane causing the tearing of the break-off line and the tilting of the membrane towards the interior volume of the body, which enables the contents to flow.
Such part is also designed to be easily produced in a simple plastic injection mold, and does not require a sliding mold.
Advantageously, the stop is formed by a protrusion projecting relative to the outer surface of the membrane.
In a first alternative solution, said stop is located on the side diametrically opposite the middle of said break-off line.
In a second alternative solution, said stop is in the middle of said break-off line.
According to a particular embodiment, said break-off line extends over an arc of circle of less than 360-A°, with A ranging from 5 to 180°.
According to a particular exemplary embodiment, said break-off line 12 extends over an arc of a circle of less than 360-A°, with A ranging from 5 to 180° and said stop is oriented in the direction opposite the interior volume, with the center line of said protrusion having a radius R, where R substantially corresponds to the median radius of the threaded neck of said container, with said protrusion 22 being on an arc of A°.
Advantageously, said hinge area, the median radius of which is greater than R, extends over an arc of at least A°.
According to an alternative solution, the membrane is extended at its lower part by a striker extending perpendicularly to the surface of the membrane.